A Generalized Analytical Approach to Evaluate the Input Current Ripple of a VSI With Space-Vector-Based PWM Techniques

Capacitors are among the most fragile components after power semiconductor devices in field operations of power electronic converter systems. Hence, the estimation of ripple current that flows through the dc bus capacitor becomes important from the reliability perspective. Switching transitions in a voltage source inverter (VSI) cause the dc-side input current to be pulsating in nature which is periodic with a finite average value. This article proposes a method to analyze this input current of a three-phase, two-level VSI in a synchronous reference frame for a given output current. The analysis can be generalized for any given space vector-based pulse width modulation technique used for inverter control. The present work also establishes the periodicity of the input current, which is essential to obtain its accurate harmonic spectrum. The proposed method is utilized to estimate the power loss and temperature rise in the dc-link capacitor of a two-level VSI connected to a front-end diode rectifier through an inductor-capacitor (LC)-filter. Simulation and experimental results support the theoretical analysis presented in this work.